This invention relates to a manually operated coffee-making machine.
Currently, there are various types of coffee makers which are based upon mutually different operating principles which are available on the market.
In particular for household use, the so-called "moka-express" coffer maker is traditionally employed which has a water storage reservoir into which a percolator holding funnel dips and which is in communication with a collecting container usually placed on top of the water storage reservoir.
With this embodiment, the coffee percolate forms by the water raising under the thrust from the pressurized steam which is generated above the water within the storage reservoir. Therefore to form the coffee percolate, it becomes necessary to supply the water under pressure, at a temperature which is consequently higher than the temperature of 100.degree. C., the boiling temperature of water at atmospheric pressure.
This design yields coffee which is not always of a high quality, both on account of its being permeated by water at a temperature which is other than optimum for the percolate to form, and because it is impossible to provide a sufficient back pressure opposing the water passage to generate, by the time the water flows through the coffee powder, a comparatively high pressure which can contribute materially to the production of a high quality coffee.
On the other hand, coffee makers for household use, wherein a reservoir, are known usually intended to accommodate cold water therein, is provided from which a pump draws the water and delivers it to a small electrical heating boiler and hence to the percolator holder assembly for percolation to take place.
With this embodiment, one can obtain the desired water pressure without having to reach thermal levels that hinder a proper coffee making procedure. However, considerable difficulties are generally encountered with the thermal control of the assembly because it is impossible or at least very difficult to achieve a proper thermal balance of all the assemblies which contribute to the making of "espresso" coffee. Thus, variations in the quality of the coffee result thereby resulting in the initial coffee dosages being of inferior quality owing to the various assemblies having not yet reached a good thermal balance.
Another drawback of prior coffee makers relates to control of the back pressure opposing delivery of the water under pressure. In particular, the back pressure is applied directly to the cake of powder coffee and is therefore dependent on various external environmental factors, such as the coffee grinding, humidity of air, atmospheric pressure, and so forth.